Undertake studies of new cell surface antigens in the mouse which appear to be detectable in both normal and tumor cells Work performed shall include: (1) Studies of Ly - 4.2: Preparation of antisera shall be continued; fluorescence studies of distribution in normal and tumor tissues shall be carried out; ontongeny of B cells, correlation of Ly - 4.2 on various cells of bone marrow origin shall be studied; studies of effects of anti Ly - 4.2 on various immune systems a and in vivo shall be undertaken. (2) Studies of Ly antigens: Production of antisera to Ly 4.1, 5.2, X.1 and other new antigens identified shall be undertaken; genetic, population, functional and other special studies shall be carried out on such antigen.